How to measure time taken by a function to execute

Question

I need to get execution time in milliseconds.

I originally asked this question back in 2008. The accepted answer then was to use new Date().getTime() However, we can all agree now that using the standard performance.now() API is more appropriate. I am therefore changing the accepted answer to this one.

Answer 1

Using performance.now():

var t0 = performance.now()

doSomething()   // <---- The function you're measuring time for 

var t1 = performance.now()
console.log("Call to doSomething took " + (t1 - t0) + " milliseconds.")

NodeJs: it is required to import the performance class

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Using console.time: (non-standard) (living standard)

console.time('someFunction')

someFunction() // Whatever is timed goes between the two "console.time"

console.timeEnd('someFunction')

Note: